How To Convert Odds To Probability

Typically, there are three kinds of odds you will come across in the sports betting landscape.

They all reflect the same thing, the return you will receive on a given amount of money placed on a bet.

Decimal odds are a simple reflection of the return you will receive for each single unit placed. In other words, odds of 1.65 means that for every 1.00 you place on a particular outcome, you will receive a profit of 0.65 should that outcome prevail.

To convert these odds to their respective implied probabilities we make a simple calculation.

1 divided by the decimal odds.

Fractional odds are generally the most traditional form of expressing betting odds. They are a simple reflection of the return you will receive for a particular amount bet. So for example, the odds of 5/2 (expressed as 5 to 2) means that for every 2 units that you bet, you will receive 5 back.

To convert fractional odds into their respective probabilities, we make the following calculation.

Denominator divided by (denominator plus numerator)

Multiplied then by 100 to express as a implied probability percentage of 28.6%.

Moneyline odds, also known as American odds are probably the most foreign odds format to those of us outside of North America. And at first they appear a little confusing. But it is helpful especially when listening to Americans speaking about gambling odds in sports broadcasts or podcasts. So, let’s see how we can convert Moneyline odds into their respective implied probabilities.

There are two instances of Moneyline odds.

The first are ‘minus’ moneylines. This is expressed as for example -120. But what does this mean exactly?

Well, it is essentially saying that to win 100 you have to make a bet of 120. In other words, if you place 120 on that outcome, you will receive a profit of 100.

The other instance are ‘plus’ moneylines. This is expressed as for example +180.  
This means that if you bet 100, you will win 180.

So how do we convert the ‘plus’ and the ‘minus’ moneyline odds into their implied probabilities?

Multiplied then by 100, we get the implied probability percentage of 54.5%.

Now the calculation for ‘plus’ moneyline odds, we make the following calculation:

100 divided by (plus moneyline odds + 100)

Multiplied then by 100, we get the implied probability percentage of 35.7%.

Knowing how to convert one form of odds to another can be helpful, especially if you have come into possession of a large amount of betting data that has odds formatted in an unfamiliar way.

To do this, we first need to convert any odds format to their implied probability. Once we have done this, the calculations are fairly straight forward.

100 divided by implied probability.

(100 divided by implied probability) – 1.

This depends on whether the implied probability is above 50% or below.

If it is above, we make the following calculation.

(implied probability divided by (100 – implied probability)) multiplied by 100.

If the implied probability is below 50%, the calculation is adjusted a little.

(( 100 – implied probability) divided by implied probability) multiplied by 100.

While there are many tools on the web that will help your odds conversion to percentage and convert odds to other formats, it is still a good practise to understand the calculations behind these conversions. This will only help you better understand what the odds represent in terms of value as well as exercising your betting brain to think instinctively in terms of implied probabilities when odds are presented to you.

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